Patent GB-1491531-A (GB)
Title: Electronic calculator clock or watch apparatus
IPC: G04G99/00
Filed: 1975-03-05
Abstract: 1491531 Electronic calculator watches OPTEL CORP 5 March 1975 [27 March 1974] 9165/75 Heading G4A [Also in Division G3] An integral electronic digital calculator/ wristwatch comprises a timekeeping circuit, e.g. a relatively low power dissipating complementary-MOS watch chip 100, and a calculator circuit, e.g. a higher power dissipating P-MOS calculator chip 200 sharing a common display, e.g. a six-digit segmented liquid crystal display 120, power being supplied to the calculator chip 200 only when the calculator mode has been selected in order to reduce power consumption. Watch chip 100.-A crystal-controlled quartz oscillator 110 operating at 32,768 Hz has its output frequency successively divided by 512 and by 64 in respective dividers 111 and 114 to produce a 1 Hz timing signal. The 1 Hz timing signal passes to a seconds counter 116 wherein sixty pulses are counted to produce and transmit an output pulse, indicative of one minute, to a minutes counter 125, the stored contents of seconds counter 116 being fed via a decoder 117 and a driver 118 to the seconds segments of display 120. Sixty output pulses from seconds counter 116 are counted by minutes counter 125 to produce and transmit an output pulse, indicative of one hour, to an hours counter 130, the stored contents of minutes counter 125 passing via a decoder 126 and a driver 127 to the minutes segments of display 120. The stored contents of hours counter 130 pass via a decoder 131 and a driver 132 to the hours segments of display 120. A setting circuit 143, fed from the divider 111, supplies timing pulses to counters 116, 125 and 130 at a rate much faster than 1 Hz on operation of a switch 144, to enable the displayed time of day to be corrected by the user. The chip is supplied with a 15 V drive voltage from a 1À5 V battery 140 via a voltage booster 141. Calculator chip 200.-The calculator mode is selected by operation of a switch 202 which sets a flip-flop 203, causing a transistor 205 to conduct and connecting the P-MOS calculator chip 200 to voltage booster 141. A keyboard encoder 211 receives input signals from a miniature keyboard (32), Fig. 2A (not shown), the input signals being converted to binary or BCD form and used to select instructions from a ROM212. The ROM 212 operates in conjunction with an arithmetic unit 215 and a RAM 216 to perform the four rules of arithemetic, the results of such calculations being stored in a buffer 221 for transmission to the display 120. At the end of a calculation, the result is transferred from buffer 221 to a storage register 160 of the watch chip, and is then displayed by display 120 for a suitable predetermined time, e.g. 15 seconds. The storage register 160 is then reset to all zeros and the time of day again shown by display 120, flip-flop 203 also being reset so that the P-MOS calculator chip 200 is disabled. Time zone control 300.-The calculator/ wristwatch has provision for changing the displayed time of day by an integral number of hours to accommodate different time zones. This is accomplished (Fig. 7, not shown) by first disabling the hours counter 130, transferring the contents thereof to a counter (680) to act as a reference hours time, obtaining the new "hours" time from a diode matrix (700), and transferring this new "hours" time to the hours counter 130 and thence the display 120. Any one of twelve different time zones may be selected by first depressing a time zone switch 301 and then a selected one of the digit or function keys on the keyboard. The reference hours time is fed to one row of the diode matrix (700) and a coded value of the key depressed to one column, the value corresponding to the thusselected crosspoint of the diode matrix being decoded and fed to the hours counter 130. An alternative embodiment is mentioned wherein time zone changes are effected by an adder/ subtractor circuit. Reference has been directed by the Comptroller to Specifications 1,405,009, 1,396,671 and 1,389,136.